The 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) is a key enzyme involved in the aromatic amino acid synthesis pathway in plants and bacteria. Glyphosate, which is also referred to as N-phosphylmethyl glycine, is a broad-spectrum, highly efficient post-sprouting herbicide. Glyphosate is a competitive inhibitor of phosphoenolpyruvate (PEP), which is one of the substrates of EPSPS. Glyphosate block the conversion of PEP and 3-phosphate-shikimate to 5-enolpyruvul 3-phosphate-shikimate catalyzed by EPSPS, thereby block the synthesis pathway of shikimic acid, a precursor for the synthesis of aromatic amino acids, and lead to the death of plants and bacteria.
The glyphosate tolerance of a plant may be obtained by stably introducing a gene encoding glyphosate-tolerant EPSPS to the plant genome. There are mainly two classes of known glyphosate-tolerant EPSPS genes: Class I (see, e.g. U.S. Pat. No. 4,971,908; U.S. Pat. No. 5,310,667; U.S. Pat. No. 5,866,775) and Class II (see, e.g. U.S. Pat. No. 5,627,061; U.S. Pat. No. 5,633,435). These genes have been successfully introduced into plant genomes, and the glyphosate-tolerant plant cells and plants are obtained.
The invention is aimed to find a novel EPSPS of native sequence that is tolerant to glyphosate.